JPH06295924A - Manufacture of liquid crystal display device - Google Patents

Abstract

PURPOSE: To avoid the current effect of a transparent electrode and reduce the contact resistance of a source/drain by depositing a heavily doped semicon ductor layer and metal on the entire surface and selectively etching to form data lines and source electrodes connected to source regions. CONSTITUTION: After continuously depositing a heavily doped n-type polycrystalline Si 11 and metal 12 such as Al, a photosensitive film 13 is coated thereon, exposed and developed. When this film 13 is developed, the electrolyte of the developer liq. will lower along the Al bank but never contacts a transparent electrode 9 as the Si 11 acts as a barriers, thus preventing the current effect. The heavily doped n-type polycrystalline Si 11 directly contacts drain/ source regions 6a, 6b to facilitate the contact resistance control. The Si 11 and metal layer 12 are laminated to form a double structure which prevents the short-circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device,
In particular, the present invention relates to a method of manufacturing a liquid crystal display element using a top gate polycrystalline silicon thin film transistor as a switching element, in which source / drain electrodes are formed by using n ⁺ polycrystalline silicon and a metal.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device (Liquid Crystal)
Display) has a structure in which liquid crystal is injected between two glass substrates on which electrodes are formed. When a voltage is applied to the electrodes to change the alignment state of liquid crystal molecules, the optical properties of the liquid crystal change. This is what is used to display an image.

The liquid crystal display device includes a simple matrix driving method using an averaging method of an operation voltage and a data signal voltage using time division driving, and an active element independent of each pixel electrode. ) (Switching element) is attached to drive each pixel independently to minimize the influence of the data signal of the adjacent pixel to enhance the contrast ratio and to increase the number of scanning lines Active matrix drive It can be roughly divided into two types. In such an active matrix driving method, a thin film transistor (hereinafter abbreviated as TFT) is used as an active element.
TFT) and polycrystalline silicon thin film transistor (Poli Silico
n TFT), and depending on the form, a stagger (Stagge
r) type, Co-planar type, Self
There are gned type and top gate type.

Among such liquid crystal display devices, a pixel structure of a conventional liquid crystal display device using a top gate type polycrystalline silicon thin film transistor as a switching device will be described with reference to the drawings. 1 to 3 are process diagrams showing a conventional method of manufacturing a liquid crystal display element of a top gate type polycrystalline silicon thin film transistor. First, as shown in FIG. 1 (a), a buffer layer (2) is formed on a transparent glass substrate (1) as an insulating film having excellent adhesive strength, and a semiconductor layer (3) is formed on the buffer layer (2). To do.

Next, as shown in FIG. 1B, the semiconductor layer
The active layer (3a) is formed by selectively removing (3) using a photoetching process so that it remains only in the thin film transistor forming region. Next, as shown in FIG. 1 (c), a gate insulating film (4) and a metal layer (5) are sequentially deposited on the entire surface, and then, as shown in FIG.
As shown in (a), the metal layer (5) and the gate insulating film (4) are selectively removed to form a gate electrode (5a) and a gate line (5b) on the active layer (3a). Where the gate line (5b)
Is the gate line (5b) for driving the thin film transistors of other pixels
Is. Next, as shown in FIG. 2 (b), the gate electrode (5a)
The source / drain region of the thin film transistor is formed by implanting high concentration n-type ions into the active layer (3a) using the mask as a mask and performing heat treatment.
Form (6a) and (6b).

Next, as shown in FIG. 2C, an interlayer insulating film is formed.
Then, (7) is deposited and the interlayer insulating film (7) is selectively etched so that the source / drain regions (6a) and (6b) are exposed to form contact holes (8). Next, as shown in FIG. 3, a transparent electrode (9) is formed in one pixel area of the thin film transistor, a metal such as aluminum is deposited on the entire surface, and a photoetching process leaves only the contact hole (8). As described above, the drain region (6b) and the transparent electrode (9) are connected to each other through the contact hole (8), and the source region (6a) and the data line (not shown) are connected to each other. A conventional liquid crystal display device was manufactured by forming a source / drain electrode 10 so as to be connected to each other.

The operation of the conventional liquid crystal display device manufactured as described above will be described. When a voltage higher than the threshold voltage is applied to the gate electrode (5a), the gate insulating film (4) and the active layer are
A channel is formed at the interface with (3a), and when a signal voltage is applied to the data line at this time, the source region and the drain region are made conductive and the signal voltage is transmitted to the transparent electrode (9). It is transmitted to and displayed (display).

[0008]

However, the conventional method for manufacturing a liquid crystal display device has the following problems. Since the source / drain electrodes (10) are connected to the source / drain regions (6a) and (6b) through the contact holes (8), the source / drain regions (6a) and (6b) and the source / drain electrodes (10) are connected. ) Is difficult to control the contact resistance with. When the source / drain electrodes (10) are formed, when the aluminum film is vapor-deposited and the photosensitive film is applied for exposure and development, the electrolyte of the developer contacts the transparent electrodes (9) along the aluminum hillocks. And current effect (Galvanin Effect)
When etching aluminum, the transparent electrode (9)
Since it may be etched together, disconnection and transparent electrode pattern formation may be incomplete. When forming the source / drain electrodes (10), a single aluminum layer (sigle layer) is used together with the data lines.
Since it is formed by, there is a possibility that the data line may be broken, resulting in low reliability. An object of the present invention is to solve the above problems,
The data line and the source / drain electrodes are formed of a high concentration n-type semiconductor layer and metal, and the current effect of the transparent electrode (Galv
anin effect), source / drain contact resistance is reduced, contact resistance is easily controlled, and data line short-circuit prevention and offset (Off-Set)
An object of the present invention is to provide a liquid crystal display device that can be structured.

[0009]

In order to achieve the above object, according to the present invention, a step of forming a buffer layer on a transparent substrate and forming an active layer in a thin film transistor region on the buffer layer; A step of forming a gate insulating film, a gate electrode and a gate line on the upper surface; a step of forming source / drain regions by implanting impurity ions into the active layer using the gate electrode as a mask; and an insulating film deposited on the entire surface. A step of forming a contact hole on the source / drain region and forming a transparent electrode on the insulating film of the pixel region, and a semiconductor layer and a metal doped with a high concentration of impurities are vapor-deposited on the entire surface. To selectively form a source electrode and a data line to be connected to the source region and to connect a drain region and the transparent electrode. And forming an in-electrode.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a liquid crystal display device of the present invention will be described in detail below with reference to the drawings. 4 to 7 are process diagrams showing a method of manufacturing a liquid crystal display device of a top gate type polycrystalline silicon thin film transistor according to the present invention. In the method for manufacturing a liquid crystal display device of the present invention, first, as shown in FIG. 4 (a), a buffer layer (2) having excellent adhesion is formed on a transparent glass substrate (1), and the buffer layer (2) is formed on the buffer layer (2). A semiconductor layer (3) is formed. Next, as shown in FIG. 4B, the active layer 3a is formed by selectively removing the semiconductor layer 3 so as to remain only in the thin film transistor forming region by using a photoetching process. next,
As shown in FIG. 5 (a), a gate insulating film (4) and a metal layer (5) are sequentially deposited on the entire surface, and then, as shown in FIG. 5 (b), a metal layer (5) and a gate insulating layer are formed. The gate electrode (5a) and gate line (5b) are formed on the active layer (3a) by selectively removing the film (4).
To form. Here, the gate line (5b) is a thin film transistor driving gate line (5b) of another pixel. next,
As shown in FIG. 5 (c), the source / drain regions (6a) and (6b) of the thin film transistor are formed by implanting high-concentration n-type ions into the active layer (3a) using the gate electrode (5a) as a mask and heat-treating. Form.

Next, as shown in FIG. 6A, an interlayer insulating film is formed.
Then, (7) is deposited and the interlayer insulating film (7) is selectively etched so that the source / drain regions (6a) and (6b) are exposed to form contact holes (8). Then, FIG. 6 (b)
As shown in, in one pixel area of the thin film transistor,
A transparent electrode (9) is formed.

Next, as shown in FIG. 6 (c), the source / drain regions (6a), (6b) are formed through the contact holes (8).
So that they are connected to each other, a polysilicon (11) doped with a high concentration of n-type impurities and a metal such as aluminum (Al) are sequentially deposited on the entire surface, and then a photosensitive film (13) is applied thereon and then the source is formed. A source / drain region is defined by exposing and developing using a pattern mask of the / drain electrode.

Next, as shown in FIG. 7, the photosensitive film (1
The metal layer (12) and polysilicon (11) using 3) as a mask
By selectively removing the layer, the source electrode and the data line in which the metal (12a) and the polysilicon (11a) are laminated so as to be connected to the source region (6a) through the contact hole (8). (Not shown), and the metal (12b) and polysilicon (11b) are connected so that the drain region (6b) and the transparent electrode (9) are connected through the contact hole (8). After forming the stacked drain electrodes, the photosensitive film (13) is removed to manufacture the liquid crystal display device of the present invention. The operation of the liquid crystal display device of the present invention manufactured in this manner is the same as that of the conventional one.

[0014]

As described above, according to the method of manufacturing a liquid crystal display device of the present invention, high-concentration n-type doped polycrystalline silicon and a metal such as aluminum are continuously vapor-deposited, and then a photosensitive film is formed thereon. When the photosensitive film is developed, even if the electrolyte of the developer drops along the aluminum mound, the polycrystalline silicon is blocked by the blocking film.
The electrolyte of the developer plays the role of cking later) and the transparent electrode
Since it cannot contact with (9), the current effect is prevented, and the high-concentration n-type doped polycrystalline silicon is directly contacted with the source / drain regions (6a) and (6b). Is reduced and control of contact resistance is facilitated.

The data line is not a single line of a metal layer, but a double structure of a source / drain electrode and a data line (11) in which a high-concentration n-type doped polycrystalline silicon and a metal layer are laminated. There is an effect that a short circuit is prevented and a set-off structure is possible.

[Brief description of drawings]

FIG. 1 is a process drawing showing a conventional method for manufacturing a liquid crystal display element of a top gate type polycrystalline silicon thin film transistor.

FIG. 2 is a process drawing showing a method for manufacturing a conventional liquid crystal display device of a top gate type polycrystalline silicon thin film transistor.

FIG. 3 is a process diagram showing a method of manufacturing a conventional top gate type polycrystalline silicon thin film transistor liquid crystal display element.

FIG. 4 is a process drawing showing a method of manufacturing a liquid crystal display element of a top gate type polycrystalline silicon thin film transistor of the present invention.

FIG. 5 is a process drawing showing a method of manufacturing a liquid crystal display element of a top gate type polycrystalline silicon thin film transistor of the present invention.

FIG. 6 is a process drawing showing a method of manufacturing a liquid crystal display element of a top gate type polycrystalline silicon thin film transistor of the present invention.

FIG. 7 is a process drawing showing a method of manufacturing a liquid crystal display element of a top gate type polycrystalline silicon thin film transistor of the present invention.

[Description of Reference Signs] 1 transparent glass substrate 2 buffer layer 3 semiconductor layer 3a active layer 4 gate insulating film 5 metal layer 5a gate electrode 5b gate line 6a source region 6b drain region 7 interlayer insulating film 8 contact hole 9 transparent electrode 10 source / Drain electrode 11, 11a Polysilicon 12 Metal layer 12a Metal 13 Photosensitive film

Claims (2)

[Claims] 1. A step of forming a buffer layer (2) on a transparent substrate (1) and forming an active layer (3a) in a thin film transistor region on the buffer layer (2), and on the active layer (3a). Gate insulating film (4), gate electrode (5a)
And a step of forming a gate line (5b), and by implanting impurity ions into the active layer (3a) using the gate electrode (5a) as a mask, source / drain regions (6a) and (6b) are formed. Process and insulating film (7) is vapor-deposited on the entire surface, contact holes (8) are formed on the source / drain regions, and the insulating film in the pixel region is formed.
(7) A step of forming a transparent electrode (9) on the upper surface, and a semiconductor layer and a metal doped with a high concentration of impurities are vapor-deposited on the entire surface, and the semiconductor layer and the metal are selectively etched and connected to the source region. Forming a source electrode and a data line as described above, and forming a drain electrode so that the drain region (6b) and the transparent electrode (9) are connected to each other. Device manufacturing method. 2. The method of manufacturing a liquid crystal display device according to claim 1, wherein the semiconductor layer is formed of polycrystalline silicon doped with a high concentration of n-type impurities.